Study On Adsorption Characteristics Of Activated Coke On SO₂ And Numerical Study On Flow Field Of Fixed Bed Reactor

Energy has always been an important material guarantee for human survival.In the 21 th century,as economic rapidly develops the demand for energy across the world rises dramatically.The abundance of coal in our country allows that it has become the fuel for over 60% of energy consumed annually,nearly 80% of which is burned and discharges its emissions into the atmosphere directly.It is difficult to reverse this situation in a short time.China’s coal-dominated energy structure has resulted in the air pollution dominated by sulfur dioxide.In the last few decades,the amount of sulfur dioxide goes into the atmosphere every year in our country is approximately20 million tons,70% of which is the result of increased industry,that makes environment problems becoming rincreasingly prominent,especially the frequent haze weather.Given this situation,it is essential to control the amount of sulfur dioxide that our country is producing.Due to the fact that the activated coke dry desulfurization possesses a plenty of outstanding advantages of saving fresh water resources,high efficiency,low cost and recycling sulfur resources and so on,it has gained much attention.Because of its wide application prospects,the research of activated coke technology is necessary.The desulfurization efficiency of activated coke is affected by many factors such as pore structure,surface functional group,metal additive,activation condition and process operating conditions.Therefore,it is necessary to understand the adsorption equilibrium and adsorption kinetics of the activated coke before designing the reactor fixed bed to determine the process operating conditions of the reactor.At the same time,in order to determine the size and power of the fan,and air volume,it is essential to study the flow field characteristics of fixed bed reactor.Therefore,based on the experimental data in [50],the adsorption equilibrium and adsorption kinetics of the activated coke were studied by using the model of adsorption isotherm,the model of internal diffusion and the model of adsorption kinetic respectively.The effects of different process parameters on the desulfurization efficiency of the activated coke were revealed.In addition,the distribution of gas flow field in the fixed bed of activated coke was simulated by numerical simulation software.The influence of the distribution range of particle size distribution,the particle arrangement,the particle size and the height of packed bed on the pressure drop of fixed bed reactor was presented.The main conclusions are as follows:(1).It was found that the Langmuir adsorption isotherm equation has better linear correlation with the measured value,and it can be used to predict the adsorption equilibrium of activated coke under other operating conditions with the interpolation method.At the same time,a multivariate regression equation is proposed to describe the relationship between the activated coke sulfur content and the operating conditions of each process.Through the analysis of the adsorption kinetics of activated coke,it was found that the mass transfer process was in accordance with the model of Lagergren.In addition,different adsorption stages were dominated by different mechanisms of adsorption.(2)According to the study on the studies on characteristics of the flow field of activated coke fixed bed reactor,it was found that:(a).The bed pressure drop of the fixed bed with broad particle size distribution was larger than that of the fixed bed with a narrow particle size distribution,while the pressure drop of the fixed bed with spherical particles was minimal.(b).The pressure drop of the fixed bed with four ways of arrangement were follows: scattered pile>α=30°>α=15°>regular arrangement.Therefore,taking into account the pressure drop of fixed bed and the efficiency of activated coke desulfurization,it was suggested that the packing arrangement form of regular arrangement should be used in the actual project.(c).The pressure drop of the fixed bed with the three sizes of were follows: 7mm>9mm>11mm,so,small particles could reduce the porosity of fixed bed and increase the pressure drop of bed.Therefore,the activated coke particle with particle size of 11 mm was selected in this paper.(d).In the six different lengths of bed,the pressure drop and operating costs of the fixed bed with the length of 400 mm was smaller and the activated coke filling capacity of it is larger.Therefore,the length of fixed bed chosen in this paper was 400 mm.